1. Field of the Invention
The invention relates to computer networks in general and, in particular, to devices and methods that monitor such networks.
2. Prior Art
The use of local area networks (LAN) for interconnecting computers, workstations or the like devices collectively called Data Terminal Equipment (DTE) is well known in the prior art. A typical LAN includes some type of communications media interconnecting the DTEs and protocols that, among other things, control transmission and reception of data on the LAN. The most popular types of protocols are ethernet, CSMA/CD Token Bus and Token Ring. Even though ethernet and CSMA/CD are different in minor respects, for purposes of discussion, they will be assumed to be substantially similar. The protocol for operating the LANs are promulgated by the IEEE Standard Committee for LANs. Specifically, the IEEE 802.3 Standard promulgates protocols for CSMA/CD LANs and the IEEE 802.5 Standard promulgates protocols for Token Ring and Token Bus.
Remote monitoring (hereafter called RMON) of LANs for problem isolation and determination has always been necessary to ensure proper operation of the LAN. Usually, the monitoring is done at a customer premises.
Initially, RMON devices were used to measure the physical parameters of the networks. Eventually, ISO layer 2 devices were used to capture a series of data bits, on the LAN, that were interpreted by the user. Each user had different requirements and each device had to be configured to measure the desired parameters and data pattern. To facilitate consistency in monitoring, the Remote Monitoring (RMON) standard (Request for Comments--RFC 1757) has been developed to provide a standard set of data parameters to be gathered and displayed on a network management workstation to determine network operation. For this information to be obtained, a device called a probe had to be attached physically to the network to be monitored. For single segment LANs, the probe can easily be attached to collect the RMON and display RMON information.
As LAN segments become more congested and/or more LANs are required to meet customers' requirements, interconnecting devices called LAN Switches are used. With the LAN Switch, separate LAN segments interconnecting a plurality of stations are connected to each port of the switch.
To gather the RMON statistics, the prior art uses two configurations. In one of the prior art configurations a probe is connected to each segment to collect the RMON statistics and generate RMON information that is displayed at the remote Management Workstation. In another prior art configuration, the RMON probe is at the Management Workstation and conductors connect the probe to each segment.
Still other examples of the prior art techniques and systems are set forth in U.S. Pat. Nos. 5,231,593; 5,251,152; 5,101,402 and articles entitled "Axon Tackles Switch Traffic Monitoring" and "Switches Integrate Monitoring" by Claudia Graziano, LAN Times (Online).
Even though the above prior art works well for their intended purposes, they are not effective when used in networks interconnected by interconnecting devices such as switches. In switch connected networks, multiple probes are required to monitor the segments. Adding probes to each segment is very costly and difficult to manage. Another problem is that in some of the prior art, such as U.S. Pat. No. 5,101,402, the statistics are gathered at the session level. The name "session level" suggests that the statistic gathering is done at layers above the layer 1 (physical) and layer 2 (data link) of the International Standard Organization (ISO) seven layer model. It is believed that gathering layer 1 and layer 2 (physical and data link) statistics are necessary for effective network management.
Still another problem which the prior art does not even recognize, much less address, is the gathering of RMON statistics and display RMON information about the internals of the switch. Such internal monitoring can be of immense importance in managing and distributing load in the network. The present invention provides internal monitoring of the switch.
Consequently, there is a need to provide an RMON device to collect layer 1 and layer 2 statistics. In addition, an integrated solution for gathering RMON statistics below the session level is required. The present invention described hereinafter, provides the needed solution.